Wild-type Cordyceps is a composite consisting of stroma of a fungus that grows on a dead caterpillar whose larva is the primary host of the fungus, which is also known as caterpillar fungus. More specifically, wild-type Cordyceps grows in a natural environment and mainly consists of stroma of Cordyceps sinensis [Berk.] Sacc. (family Hypocreaceae) and a dead caterpillar of Hepialus armoricanus (family Hepialidae). It is one of the most famous and most expensive traditional Chinese medicinal materials. It is restrictedly distributed in alpine habitats on the Tibetan Plateau in China.
Wild-type Cordyceps proved to have various therapeutic effects on the renal system, the respiratory system and the immune system. For example, those effects include: tonifying the kidney, replenishing the lung, stanching bleeding and resolving phlegm and mucus. Cordyceps has been historically used for the treatments of hyposexualities, hyperglycemia, hyperlipidemia, asthenia, respiratory disease, and renal dysfunction, etc. (e.g. Zhu, J. S. et al., J. Altern. Complem. Med. 1998, 4 (3), 289-303; and Zhu, J. S. et al., J. Altern. Complem. Med. 1998, 4 (4), 429-457). In addition to the medical applications, Cordyceps is also widely utilized as a tonic and functional food in China (Zhu, J. S. et al. J. Altern. Complem. Med. 1998, 4 (3), 289-303).
The broad spectrum of pharmacological effects of wild-type Cordyceps has led to an ever-increasing demand on this herbal medicine whose natural resource is increasingly scarce. To meet the increasing demands of wild-type Cordyceps, several products based on fungi or mycelia isolated from wild-type Cordyceps and being artificially cultured have been developed and manufactured in large quantities in particular by using fermentation technology. Five of such alternative products have been approved so far as drugs by the China Food and Drug Administration (CFDA), comprising Cordyceps sinensis, Hirsutella sinensis, Cephalosporium sinensis, Mortierella SP and Gliocadium roseum. According to the data from the National Bureau of Statistics of China, the annual production of these mycelia was over 3000 tons in 2011, demonstrating a wide application and recognized therapeutic effects of these mycelial products. As alternatives of wild-type Cordyceps, Cordyceps derivates have been substantially investigated for their pharmacological effects. Studies have shown that the mycelial component could invigorate the lung and nourish kidney, improve the heart health and the liver health, as well as strengthen the immune system, etc. (for example Weng C. M., Chin. J. Inf. Tradit. Chin. Med. 2000, 7 (4), 75-76 or Wang Z. H. et al., Chin. J. Clin. Med. 2003, 3 (8), 681-682). Usually different conditions for culturing the fungi or mycelial strains are applied for production of these derivates, wherein variations in fermentation time, temperature and culture medium could be accompanied by differences in the ingredients which, thus, make quality and quantity control to very important means for ensuring safety and efficacy of a treatment with Cordyceps. 
However, comprehensive studies on chemical constituents of wild-type Cordyceps compared to the above mentioned products based on isolated and artificially cultured fungi or mycelia are still absent. Currently, nucleosides, mannitol and amino acids which are, however, not the specific constituents of either the derivates or wild-type Cordyceps were used as markers for the quality control. In addition, the reported bioactivities of the above constituents are not fully responsible for the observed effects. The aforesaid non-specific constituents cannot reflect the true quality level of the wild-type Cordyceps and the above mentioned products being tested, let alone facilitate the identification and differentiation between wild-type Cordyceps and available alternative products. These limitations highlight the importance of identifying more specific and active constituents which can be used for quality control and thus methods allowing for identifying of and differentiating between wild-type Cordyceps and the mentioned alternative products.
Sphingolipids (SPLs) are a complex family of compounds that share a common structural feature, i.e. a sphingoid base backbone which could be biosynthesized from serine and a long-chain fatty acyl-CoA. The sphingoid base backbone can be subsequently converted into ceramides, phosphosphingolipids, glycosphingolipids and other subgroups of sphingolipids (Fahy, E. et al., J. Lipid Res. 2005, 46, 839-861).
In 1994, myriocin, a natural sphingolipid, was isolated from the culture broth of Isaria sinclairii (the imperfect stage of Cordyceps sinclairii) as a potent immunosuppressive constituent (Fujita, T. et al., J. Antibiot. 1994, 47, 208-215). Starting from myriocin, FTY720 was synthesized and finally developed into a drug (Fingolimod) for the treatment of multiple sclerosis and organ transplantation. Thus, SPLs might be active constituents of wild-type Cordyceps and respective derivates. Further studies have demonstrated the crucial role of endogenous SPLs in various biological procedures. Specifically, the natural and chemically synthesized SPLs can exert significant bioactivities. For instance, sphingoid bases have been regarded as potential anticancer agents, as represented by safingol (Schwartz, G. K. et al., Clin. Cancer Res. 1997, 3, 537-543; Coward, J. et al., Autophagy 2009, 5, 184-193) and 1-deoxysphinganine (Schoffski, P. et al., Cancer Chemoth. Pharm. 2011, 68, 1397-1403; Baird, R. D. et al., Mol. Cancer Ther. 2009, 8, 1430-1437), both of which are being evaluated in phase I clinical trials. A recent study also suggested that structural analogues of ceramide (C16-serinol) and exogenous natural ceramide exhibit promising anticancer effects (Bieberich, E. et al., Biol. Chem. 2000, 275, 177-181; Stover, T. C. et al., Clin. Cancer Res. 2005, 11, 3465-3474). Additionally, there is evidence showing that sphingomyelin has effects on the post-initiation development of preneoplastic lesions in the rat colon (Exon, J. H., South, E. H., Food Chem. Toxicol. 2003, 41, 471-476). Although this suggests that natural SPLs are pharmacologically active constituents of natural medicines, there remain challenges in identifying SPLs in a natural material or products, especially in specifically profiling SPLs including low abundance ones while clearly differentiating between them for quality and quantitative control.
Accordingly, there remains a strong need for methods which allow for identifying and quantifying components such as in wild-type Cordyceps and alternative products in particular for identifying wild-type Cordyceps and differentiating between them and alternative products as means for ensuring quality and safety of the respective treatment with Cordyceps. 